1. Field of the Invention
The present invention relates to liquid sampling valves for sampling a definite quantity of liquid samples like blood, and more particularly to a liquid sampling valve provided with a cleaning function and intended for stabilizing the operation of analyzers for a long period.
2. Description of the Prior Art
Analyzers like a hemocyte counting apparatus use a liquid sampling valve for sampling liquid samples to extract a definite quantity of such liquid samples in a tubularly configured portion like a column.
Referring to FIGS. 8 and 9, a brief description is given on the construction and the operation of conventional liquid sampling valves for general use. These liquid sampling valves usually comprise two fixed elements 10, 14 and one movable element 12 sandwiched between the two fixed elements 10, 14. FIGS. 8 and 9 show two states of liquid sampling valves.
Referring to FIG. 8, liquid samples flow in the direction of an arrow A, namely through a pipette 15, an inflow passageway Q1, a measuring passageway P1, and an outflow passageway R1 to be filled in the measuring passageway P1 (referred to as a first state). The movable element 12 moves (rotates through a predetermined angle around a horizontal rotation axis) to a state shown in FIG. 9 (referred to as a second state). Samples filled in the measuring passageway P1 in the first state are conveyed in the direction of an arrow B from the passageway S12 to the passageway S11 and then to the outside of the sampling valve along with a definite quantity of diluent liquid so that liquid samples are diluted by a definite rate.
In conventional liquid sampling valves, the contact surfaces of the fixed elements and the movable element are gradually stained with samples along with an increase in the frequency of usage. When the contact surfaces are stained to a certain degree, disadvantages occur such as leakage of liquid samples from the contact surfaces, which prevents a favorable sampling operation. Conventionally, sampling valves have been regularly decomposed so that the contact surface of each element is cleaned with a cleaning liquid thereby preventing an unfavorable operation.
Liquid sampling valves intended for automation of self-cleaning are described in the following U.S. Patent Publications.
1) U.S. Pat. No. 4,702,889 (corresponding to Japanese Published Unexamined Patent Application No. SHO. 63-502454)
2) U.S. Pat. No. 4,726,932 (corresponding to Japanese Published Unexamined Patent Application No. SHO. 60-94122)
3) U.S. Pat. No. 4,957,008
4) U.S. Pat. No. 4,822,569
All the sampling valves disclosed in the above patent publications provide a passageway (passage or channel) or a groove on the surface of the element to permit a cleaning liquid to flow therethrough.
Publication 1) describes a liquid dilution and transfer valve including an outer element provided with a cleaning passageway on the periphery thereof, the cleaning passageway intercepting a leakage liquid followed by flowing a cleaning liquid therethrough to wash away the leakage liquid.
Publication 2) describes a dosing and mixing apparatus for fluid media including an internal isolating element provided with a pair of concentric channels (first and second annular channels, the second annular channel being spaced radially outward of the first annular channel) on the surface thereof as well as a radially aligned cross channels interconnecting with the first and the second annular channel thereby immediately cleaning the surface which a liquid sample contact when the liquid sample is portioned out.
Publication 3) describes a fluid sampling, metering and transfer valve assembly comprising a pair of outer stationary valve disc elements spaced apart from each other, an inner rotatable valve disc element sandwiched therebetween, and wash means comprising a pair of radially spaced circumferential concentric grooves formed along the inner and outer portions of the interior facing surfaces of at least one of outer valve disc elements, the rotatable valve disc element being rotated 360 degrees whereby to clean the facing interior surfaces of the valve assembly.
Publication 4) describes a rotary shear valve comprising two stators (front and rear stators), a first circumferentially-extending concave arced groove formed in the rear face of the front stator and a second circumferentially extending concave arced groove formed in the front face of the rear stator wherein a cleaning solution is incorporated in a third rotary position.
The sampling valve disclosed in Publication 1) cannot produce a sufficient cleaning effect because leakage material is merely intercepted in the channel and washed away.
Publications 2) and 3) describe a radially aligned concentric grooves that traverse each passageway of the sampling valve so that a cleaning liquid to be flowed in the grooves also comes into each passageway. In other words, a liquid for diluting liquid samples in the passageways and a cleaning liquid for cleaning such passageway contaminates each other (cross contamination) there. Consequently, when the cleaning liquid is different from a diluting liquid, there arises a problem that the cleaning liquid produces an unfavorable effect on liquid samples (cells such as hemocytes).
In addition, the liquid sampling valve disclosed in Publication 2) is restricted by the position of each passageway simply because radially arranged grooves are provided in such a manner that grooves traverse the passageways. In other words, the liquid sampling valve has a drawback that the position of the passageways cannot be freely set.
Furthermore, sampling valves described in Publications 3) and 4) require a special movement of elements for the cleaning operation. In Publication 3), elements are rotated once whereas in Publication 4) elements are rotated to the third rotary position.
The object of the present invention is to provide a liquid sampling valve producing a high cleaning effect free from restrictions on the arrangement of passageways and requiring no special movement for cleaning operation wherein a cleaning liquid does not produce an unfavorable effect on liquid samples owing to cross contamination of the two different kinds of liquids.